Some printing systems have a reservoir to store printing fluid, such as ink, and a supply system to supply the printing fluid from the reservoir to a printhead, to enable the printhead to apply the printing fluid to a substrate to form an image on the substrate during a print job. The printing fluid may comprise pigment, which lends color to the printed image. The pigment may comprise particles, such as solid and/or opaque particles, that are suspended in the printing fluid.